Stefano ProfumoStefano ProfumoUC Santa CruzUC Santa Cruz

Santa Cruz Institute for Particle PhysicsSanta Cruz Institute for Particle Physics

T.A.S.C. [Theoretical Astrophysics in Santa Cruz]T.A.S.C. [Theoretical Astrophysics in Santa Cruz]

TeV Particle Astrophysics 2009

SLAC National Accelerator Laboratory, Menlo Park, CA,

July 13-17, 2009

New Physics with ACTsin the Fermi Era

Annihilation debris: an unavoidable

consequence of thermal WIMPs

Gamma Rays

1. “Primary”

• Hadronization, 0

• Final State Radition (e.g. L+L- )

(included in e.g. DMFIT)

• “Intermediate State” Radiation

(model-dependent, incl. in DSv5)

• Loop-suppressed radiative

annihilation modes (, Z, h, …)

Credit: Fermilab Website

1. Source TermdE

EdN

m

xxEQ e )(

v)(

),( rel2DM

2DM

2. Transport Equation ),(),(),( xEQdE

dnxEb

EdE

dnxED

dE

dn

teee

WIMP annihilation also produces stable Electrons and Positrons,which diffuse and loose energy

Inverse Compton off CMB and starlight photons, Bremsstrahlung and Synchrotron emission

produce radiation from radio to gamma-ray frequencies

3. Compute the Signals (IC off CMB/starlight, Synchrotron emission,…) ),(EQ xEne

Gamma Rays

1. “Primary”

2. “Secondary”

• Inverse Compton (e+e+)

(where from CMB, starlight, IRB…)

• Bremsstrahlung

• Synchrotron (for large enough B)

Credit: Fermilab Website

Annihilation debris: an unavoidable

consequence of thermal WIMPs

The multi-wavelength spectrum expected from a 41 GeV “bino” annihilating in the Coma cluster

Colafrancesco, Profumo and Ullio (2005)

“Environment”-dependent

(B, gas density, diffusion)

Set by the

DM particle

mass scale

What is “magic” about gamma-ray telescopes

for the search for dark matter?

~m

~ m-2

~ m2

~ m2/mZ4

~ 1/ ~ m-2

Baltz (2004)

They probe the energy range where

the thermal cold DM mass scale is

WIMP Mass

RangeSecondary & Low-E

Primary Radiation

Non-thermal

Production

Gamma-Ray

“Debris”

What is “magic” about gamma-ray telescopes

for the search for dark matter?

an “old”

Morselli plot

WIMP Mass

RangeSecondary & Low-E

Primary Radiation

Non-thermal

Production

What is “magic” about gamma-ray telescopes

for the search for dark matter?

Role of ACT’s in

the multi-frequency

siege to dark matter

in the Fermi Era

1. Dwarf Galaxies

2. GalaxyClusters

3. GalacticCenter

4. Cosmic RayElectrons/Positrons

1. Dwarfs: a lesson from CACTUS

Solar Array ACT located at Solar Two,

Daggett (CA), operated by UC Davis in ’04-’05

Observed PSR/SNR (Crab, Geminga),

AGN (Mk421, 501) and dSph Draco

Reported GR excess from Draco, later attributed to problems with noise assisted trigger threshold connected to starlight

dSph are DM dominated and GR-quiet objects: the usual suspect, DM interpretation of the excess

L.Bergstrom & D.Hooper, hep-ph/0512317 and S.Profumo & M.Kamionkowski, astro-ph/0601249

An important lesson: dSph are ideal targets for indirect DM searches

Moreover: ACTs are complementary to satellite-based GR telescopes[EGRET didn’t detect Draco]

1. Dwarfs: a lesson from CACTUS

S.Profumo & M.Kamionkowski, astro-ph/0601249

Exc

ess

Cou

nts

!!!

1. Dwarfs: general features of Fermi vs ACTdark matter search sensitivity

CACTUS signal huge cross section

ACT Limitation: low-energy threshold

ACT Asset: Great sensitivity to final states producing hard GR spectrum!

1. Dwarfs: Fermi results (T. Jeltema’s talk)

* Asset of Fermi: sensitivity to Inverse Compton Gamma Rays!

* Large Uncertainties on Diffusionin small extragalactic systems!

Preliminary

1. Dwarfs: Comparing MAGIC and Fermi

* Even without IC, the Fermi survey-modegives it an edge over ACTs

* Comparable sensitivities for m~1 TeV,~100h ACT obs. time

Preliminary

1. Dwarfs: prospects for ACTs in the Fermi era

Is it worth it forACTs to observe

local dSph to searchfor DM in the

Fermi era?

YES: one example:DM model that fitspositron excess

TeV particle

Large Diffusion in dSph

makes ACT much

better than Fermi!

Another example:Standard Neutralino-

type DM particle,negligible IC

m~1 TeV, comparablesensitivities for Fermi vs ACTs

m~5 TeV, ACTs canoutperform Fermi

1. Dwarfs: prospects for ACTs in the Fermi era

2. Clusters: a new gamma-ray source class?

* Largest bound dark matter structures

* Non-thermal activity detected as synchrotron radio emission

* Likely source of gamma rays from hadronic or leptonic primary cosmic rays

* Not conclusively detected so far in gamma rays

* Excess hard X radiation detected in a few cases

Galaxy Cluster Abell 1689 Warps Space Credit: N. Benitez (JHU)

2. Clusters: non-thermal activity from cosmic rays

Ophiuchus cluster (hard X-ray from Integral, new radio data)

Leptonic Scenarios alone fail to provide self-consistent explanation

Potential complementarity between Fermi and ACTs

Perez-Torres, Zandanel, Guerrero, Pal, Profumo, Prada and Panessa (2009)

2. Clusters: new physics versus cosmic rays

Signal from DM and from CR

in local clusters of galaxies

predicted to be comparable!

Jeltema, Kehaijas and Profumo (2009)

2. Clusters: new physics versus cosmic rays

Jeltema, Kehaijas and Profumo (2009)

Most promising targets for

New Physics: nearby

(gas-poor) galaxy groups!

2. Clusters: ACT and Fermi searches

H.E.S.S. Collaboration, A&A, astro-ph 0907.0727 (~8h observations)

2. Clusters: ACT and Fermi searches

See Tesla Jeltema’s talk; paper in preparation by Fermi Coll.

More targets, biased

towards those where

the DM/CR ratio is

larger, and brighter

Again, Fermi signal

dominated by IC,

HESS by FSR

Preliminary

3. The Milky Way Center and fundamental physics

Rich and complicated Region, with several sources,

large diffuse emission, non-thermal activity

3. The Milky Way Center and fundamental physics

ACT and Fermi observations of Sag A* of fundamental importance

to understand background to the (possibly) brightest DM source

3. The Milky Way Center and fundamental physics

Jeltema and Profumo (2008)

In the limit of perfect control over the diffuse and Sag A* “background”

Fermi can determine fundamental properties of DM from the GC

Regis and Ullio (2008)

Self-consistent treatment of both the Sag A* source and DM emission

must however include a multi-wavelength approach

3. The Milky Way Center and fundamental physics

Regis and Ullio (2008)

With certain assumptions on magnetic fields at the GC,

and on the DM annihilation final state

Radio and X-ray data put the gamma-ray emission beyond Fermi sensitivity,

marginally detectable by a CTA

3. The Milky Way Center and fundamental physics

4. Electrons and Positrons

Great data delivered by H.E.S.S.

on high-energy e+e- flux

Help understanding spectrum

and origin of HE e+e-

Relevance to New Physics:

1. Claim of anomalousfeatures related to e+ excess

2. Feeds back to diffusegalactic gamma ray emission

Bottom line of Fermi

e+e- analysis:

* Hard spectrum

* Compatible with

diffuse CR models

* Positron excess

requires extra

primary source

4. Electrons and Positrons

Is there an “anomalous feature” in the Fermi data alone?

Is there a residual “anomalous spectral feature”

in the Fermi data?

Most probably NO: in the ~ TeV range

• CR Source Spectrum Cutoff• Diffusion Radius comparable to mean SNR separation source stochasticity effects! [breakdown of spatial continuity and steady-state hypotheses]

1- band for largeset of random

SNR realizations

4. Electrons and Positrons: role of ACT’s

• Maximize overlap with Fermi data at >TeV

• Check for potential Anisotropy?

• Cross check HESS results with other ACT

• Re-calibrate ACT results after Fermi data with GR sources

• Follow-up on potential local sources of e+e-

ConclusionsNew Physics with ACTs in the Fermi Era

• Complementary Observations

(e.g. dwarfs, clusters, GC, e+e-)

• ACTs: Potential for Discovery

even in Fermi era

(e.g. clusters as new GR sources, dwarfs)

• Fundamental to understand

and control Background

(e.g. clusters, GC, e+e-)